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Objective. To explore the anatomic relationship between the aorta and the spine in patients with thoracolumbar/lumbar kyphosis secondary to ankylosing spondylitis (AS).

Summary of Background Data. The lumbar spinal osteotomy has been widely adopted for the correction of thoracolumbar/lumbar kyphosis caused by AS. During this procedure, the aorta may be stretched at the osteotomized level and in proximity to the tip of the pedicle screw, both of which imply a potential risk of the aortic injury. To date, no reports have been specifically published for describing the position of the aorta relative to the spine in patients with AS with fixed thoracolumbar/lumbar kyphosis.

Methods. Thirty-three patients with AS with thoracolumbar/lumbar kyphosis and 38 age- and sex-matched patients with a normal spine were included in this study. For each subject, the left pedicle-aorta angle and distance were measured from T9 to L3 on the computed tomographic scans. Radiographs were analyzed to measure the global kyphosis, lumbar lordosis, and to record the apex of the kyphotic curve.

Results. At T9-L3 levels, patients with AS with thoracolumbar/lumbar kyphosis exhibited significantly smaller left pedicle-aorta angles (from 10.23° to −11.56°) and larger distances (from 39.0 to 55.5 mm) than those with a normal spine. With increased global kyphosis, the aorta shifted more laterally to the right at periapical levels (L1 and L2, P < 0.05). Notably, the aorta was located at the middle front of the vertebrae at T12–L1 levels and far away from the vertebrae at L2 and L3 levels.

Conclusion. In patients with AS with thoracolumbar/lumbar kyphosis, the aorta is positioned more anteromedially relative to the vertebral body than that in the normal subjects. The aorta is far away from the vertebral body at L2 and L3 levels, thus it could be much safer to perform osteotomy below L1.

Level of Evidence: 4

This study, for the first time, quantified the anatomic location of aorta relative to the thoracolumbar/lumbar vertebrae in patients with ankylosing spondylitis. Compared with the normal subjects, the aorta is positioned more anteromedially relative to the vertebral body from T9 to L3 in patients with ankylosing spondylitis with thoracolumbar/lumbar kyphosis.

From the Department of Spine Surgery, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China.